This invention relates to the art of reducing work, typically reducing of billets to rods or bars or rods to wire, by rolling with rolls and has particular relationship to the structure of roll assemblies for this purpose. The rolls may be composed of materials of appropriate types, including iron or steel, capable of effecting the reduction but of particular interest are rolls of metalloids of the tungsten carbide type. The expression "of the tungsten carbide type," as used in this application, primarily means tungsten carbide and its alloys. It also means other hard metalloids such as titanium carbide, molybdenum carbide, tantalum carbide, niobium carbide, and numerous others including borides, silicides, nitrides and the like and their alloys. For a list of these metalloids, reference is made to Goetzel U.S. Pat. No. 2,581,252.
In a roll assembly the rolls are mounted on an arbor and are rotated in engagement with the work to be reduced. In the interest of concreteness, this invention will be described herein as applied to the reduction of rods. To effectively reduce the rods it is necessary that the rolls apply high compressive tangential stresses to the rods and the reactive forces on the rolls are equally high. A high torque tending to rotate each roll on its arbor is thus applied. It is an object of this invention to suppress such rotation.
In accordance with the teachings of the prior art (typically Rackoff, et al., U.S. Pat. Nos. 3,432,902, 3,574,252) lateral force parallel to the arbor axis is applied to the roll by a nut which is screwed onto the arbor and compresses the roll against a flange extending from the arbor. For rolls of large diameter and for the reduction of very hard or tough materials, the force applied by the nut, or which can be applied by a nut, is inadequate. It has also been proposed, in accordance with teachings of the prior art (Hufnagl U.S. Pat. No. 3,793,869, JETNUT hydraulic nuts), to apply the lateral force hydraulically. A piston or pad slideably in an annular cylinder is urged under hydraulic pressure into engagement with a roll. Typically, the piston is sealed against leakage of the hydraulic fluid by an O-ring of neoprene or the like. This prior art practice has not proved satisfactory because of the leakage of the hydraulic fluid and the deterioration of the O-ring gasket by the fluid, particularly at high temperature, typically above 200.degree. to 300.degree. F.
It is an object of this invention to overcome the disadvantages of the prior art and to provide a roll assembly in which the reactive torque applied to the rolls by the work is very high, but the rolls are prevented from rotating relative to the arbor by applying lateral forces to the rolls hydraulically without O-rings subjected directly to the fluid and without experiencing leakage of the hydraulic fluid.